1. Field of Invention
The invention relates to a dual-band inverted-F antenna and, in particular, to the dual-band inverted-F antenna, which has reduced dimensions and increased operation bandwidth.
2. Related Art
Antenna is a key element for transmitting and receiving the magnetic wave in the wireless communication system. Without the antenna, the wireless system could not transmit and receive information. As a result, the antenna plays an important role in the wireless communication. Choosing a proper antenna not only is helpful to match up with the outward appearance of products, but also can improve the signal quality of the transmission or reception. Moreover, a proper antenna also can reduce the production cost. According to different product application, the antenna can be designed in various ways and made of various materials. Besides, the usable band is different in every country. Therefore, there are lots of points should be considerated. At present time, IEEE 802.11, DECT, and 802.15.1 (Bluetooth) are common standards of the usable bands. Among them, the usable band for DECT is 1.88 GHz, and that for Bluetooth is 2.4 GHz. The 802.11 includes 802.11a and 802.11b/g standards, which has the band of 5 GHz and 2.4 GHz respectively.
In the prior art, the antenna body is made of a coaxial cable or a printed circuit board. Because of the material and the structure of the conventional antenna, it is high cost to produce the antenna. In addition, the dimension of the conventional antenna is not easily minimized, and the performance thereof is hardly controlled.
Recently, dual-band inverted-F antennas have been developed. It's very common to be applied in the wireless communication system, since its small dimension, simple structure, and good gains.
According to FIG. 1, the conventional dual-band inverted-F antenna 1 for receiving or transmitting signals has a radiation patch 11, a shorting pin 12, a feed point 13, and a ground plate 14. In this case, the shorting pin 12 is disposed on one side of the radiation patch 11 and the radiation patch 11 electrically connects to the ground plate 14. The feed point 13 connects a feed node of the radiation patch 11 to the ground plate 14. Thus, the inverted-F antenna 1 is obtained.
For the inverted-F antenna to receive or transmit the signals in some bands, a current should be fed in from the feed point so as to induce resonance in the radiation patch 11. Utilizing the generated band according to resonance, the antenna can receive or transmit signals of specific band. Additionally, if another radiation patch (not shown) is disposed on the radiation patch 11 through a connecting portion, the inverted-F antenna could be applied to two different bands.
As described above, the band of the conventional inverted-F antenna only covers some ranges. Consequently, different countries have different limitations in the usable bands. The inverted-F antenna products cannot be applied into different country areas. In additional, it's hard to minimize the dimension of the antenna applied for the smaller electronic products.
Therefore, it is an important subjective to minimize the dimension of the inverted-F antenna, increase the effective bandwidth of the inverted-F antenna, and manufacture the inverted-F antenna products, which can meet needs of more countries.